1. Field of the Invention
This invention relates to a warp-knit tape, for slide fasteners, in which an element-mounting edge portion is knitted simultaneously with a knit web portion so as to bulge along one longitudinal edge of the web portion.
2. Description of the Related Art
There are various types of warp-knit tapes for use known in the field of slide fasteners. For example, Japanese Utility Model Publication No. SHO 56-16088 discloses a warp-knit fastener tape which comprises a web portion knitted by knitting needles on only one of front and back sides of a multi-row-needle knitting machine, an element-mounting edge portion including double tricot stitches knitted by multiple rows of needles so as to surround a reinforcing core tightly, and a connecting portion extending between the web portion and the element-mounting edge portion and having double chain stitches knitted on both front and back sides also by multiple rows of needles. In the known fastener tape, the connecting portion has a great thickness compared with the web portion, and the element-mounting edge portion bulges uniformly from both the front and back sides of the connecting portion. With the resulting fastener tape, it is possible to mount fastener elements astride the element-mounting edge portion in a proper attaching posture and it is also possible to secure an adequate thickness of the tape portion to be clamped between opposite legs of the individual fastener elements so that the fastener elements can be attached to the tape reliably by clinching.
However, generally, the hollow to be defined between opposite legs of the individual fastener element attached to the fastener tape by clinching is substantially oval, and the oval-shape element portion is mounted astride the bulged tape portion with its distal ends gripping the web portion firmly.
Not only in the fastener tape disclosed in the above-mentioned prior art publication but in the conventional tape of this type, the cross-sectional shape of the element-mounting edge portion is substantially circular or oval in general. Accordingly, the inside surfaces of the opposite legs of the individual fastener elements act in only a limited gripping force such as to resiliently deform the element-mounting edge portion from circular into oval in cross section so that the degree of strength of attaching the elements to the tape chiefly depends on the gripping force of the distal ends of opposite element legs. Consequently, the coupling head of the individual fastener element tends to move longitudinally of the tape about the distal ends of the opposite element legs, thus obstructing smooth movement of a slider and causing a nonstable attaching posture of the fastener elements.
Further, since the cross section of the element-mounting edge portion of the fastener tape is circular or oval, it is difficult to mount, for example, a zigzag-shape row of synthetic resin fastener elements in a proper posture on an arcuate surface of the element-mounting edge portion when the fastener elements are sewn to the fastener tape.